Reusable C building blocks with an in-repo tester tuned for 42 project evaluations.

1. At a Glance
2. About This Library
3. Subject Compliance
4. Repository Layout
5. Build & Integration
6. Usage Guidelines
7. Feature Deep Dive
8. Input & Validation
9. Rendering & Output
10. Internal Architecture
11. Tester Workflow
12. Results & Reporting

Highlights: Static C library covering all mandatory libft calls plus field-tested helpers.

• Ships 40+ string, memory, FD, conversion, and list routines backed by libft.a.
• Adds practical extras (ft_atol, ft_isnumeric, ft_max, ft_str_append_char) proven useful in later 42 milestones.
• Bundles local copies of printf/ and gnl/ so dependent projects link without external fetches during defense.
• Includes a colorized regression tester under .testers/libft to preflight submissions.

Highlights: Norm-compliant foundations with pragmatic ergonomics.

• Written in pure C, respecting 42 Norm guidelines and minimal dependencies (standard headers only inside libft/).
• Favors readability: short helpers like ft_words_counter keep complex flows (e.g., ft_split) approachable for peer review.
• Optional utilities sit alongside mandatory functions but remain header-gated so downstream repos can opt in selectively.
• Memory ownership is explicit—every allocator returns heap pointers that callers must release (tester cross-checks accidental leaks).

Highlights: Matches the scope mandated in docs/subject_libft.pdf while flagging deviations.

• Mandatory Part 1/2 functions mirror prototypes and behavior described on pages 7–12 of the subject PDF.
• Bonus linked-list API implements the full t_list toolchain in libft/, meeting bonus segregation rules.
• Makefile exposes all, clean, fclean, and re, compiles with -Wall -Wextra -Werror, and avoids needless relinks via object caching in obj/.
• Extra helpers stay within subject constraints; only ft_swapstrs currently behaves as a pointer swap stub (planned refinement noted below).

Highlights: Flat structure keeps evaluation navigation fast.

• docs/subject_libft.pdf — official 42 brief kept alongside the repo for audits.
• libft/ — implementation sources plus libft.h covering mandatory and bonus APIs.
• .testers/libft/ — tester harness (tests.c, functions/, run_tests.sh, results.txt).
• printf/ & gnl/ — local working copies cloned once, stripped of history, ready for downstream linking.
• obj/ — build artifacts created by the Makefile; safe to delete via make clean.
• libft.a — compiled static archive; regenerated on each make.

Highlights: Default target prepares dependencies then produces libft.a.

• make ensures printf/ and gnl/ exist (cloning only if missing), creates obj/, and archives every .o into libft.a.
• make clean clears objects, make fclean also removes libft.a plus the cloned dependency folders for a true fresh start.
• make re chains fclean then all, rebuilding the full toolchain in one go.
• Compilation stays deterministic: no hidden flags, and every translation unit uses the same warning set.

make          # build libft.a (clones printf/gnl if absent)
make clean    # remove obj/
make fclean   # clean + remove libft.a, printf/, gnl/
make re       # force pristine rebuild

Highlights: Intended for reuse across 42 repos without manual tweaking.

• Include with #include "libft/libft.h" or adjust include paths to suit your project layout.
• Link the archive via cc your_main.c ../libft.a or add -L/-lft flags inside larger build systems.
• Keep helper usage optional: if a downstream subject forbids extras, only call functions present in the official PDF.
• Re-run .testers/libft/run_tests.sh after edits; failed cases flag mismatches immediately through results.txt.

Highlights: Modular helpers organized by use case.

• String toolkit ranges from safe copying (ft_strlcpy, ft_strlcat) to builders (ft_strjoin, ft_strtrim, ft_split).
• Memory primitives (ft_memset, ft_bzero, ft_memcpy, ft_memmove, ft_calloc) offer low-level control without hidden allocations.
• Numeric conversions include defensive parsing (ft_atoi, ft_atol) and formatting via ft_itoa for FD output helpers.
• Linked-list suite (ft_lstnew through ft_lstmap) follows the subject spec, with tester coverage for iterator/map corner cases.

Highlights: Tolerant parsing with explicit whitespace handling.

• ft_iswhitespace and ft_isspace distinguish control-space vs. literal space to tune tokenizers.
• ft_atoi rejects duplicate leading signs (--, ++) to avoid silent UB before conversion.
• ft_atol mirrors that behavior for wider ranges, enabling safe bounds checks before casting back to int.
• ft_isnumeric treats standalone signs as invalid, ensuring only well-formed numeric strings pass validation.

Highlights: File-descriptor oriented presentation utilities.

• ft_putchar_fd, ft_putstr_fd, ft_putendl_fd, and ft_putnbr_fd centralize writes for stdout/stderr or custom descriptors.```sh cd .testers/libft ./run_tests.sh

- Tester fixtures open temp files to confirm exact byte sequences and clean them post-run.
- `ft_strmapi` and `ft_striteri` support character-by-character transformations, handy before printing formatted strings.
- Combined with `ft_printf` (bundled sibling repo), `libft.a` covers both low-level writes and formatted output pipelines.

## Internal Architecture
> **Highlights:** Simple directory discipline keeps maintenance low.
- `libft.h` declares every public symbol and `t_list` struct, keeping prototypes centralized for IDE assistance.
- Object files live in `obj/` with filenames derived via `$(notdir ...)`, preventing collisions across modules.
- The Makefile defers `lib` compilation until directories exist, ensuring `printf/` and `gnl/` remain in sync without recursive makes.
- Bonus sources share the primary folder; `_bonus` naming is unnecessary because the subject allows this layout for libft.

## Tester Workflow
> **Highlights:** Mirrors evaluator behavior start-to-finish.
- Builds a test binary (`tests`) alongside `libft.a`, keeping artifacts inside `.testers/libft` for easy cleanup.
- Executes every function suite sequentially, writing verdicts to `results.txt` for archival or sharing with peers.
- Highlights failures immediately with expected vs. actual values in the same line for quick debugging.
- Relies on `libbsd` only for reference implementations (`strlcpy`, `strlcat`); macOS users already have them in libc.

<details>
<summary>Extending coverage</summary>

- Add new `.c` files under `.testers/libft/functions/` and declare their prototypes in `tester.h` to include them in the sweep.
- Re-run the script; the `find` command auto-discovers added tests without touching the Makefile.
</details>

## Results & Reporting
> **Highlights:** Actionable logs without noise.
- `results.txt` collects one line per function (SUCCESS/KO with context) so reviewers can skim outcomes quickly.
- `run_tests.sh` streams colored copies of those lines to stdout and ends with a success/total tally.
- Failures display expected vs. actual payloads (buffers, substrings, numeric values) to reduce reproduction time.
- Clean-up step deletes temporary FD fixtures, keeping the tester tree tidy between runs.

```sh
sed -n '1,10p' .testers/libft/results.txt   # quick glance after a run